JPS60158932A - Manufacturing method of flat tube heat exchanger - Google Patents

Abstract

PURPOSE:To join tightly fins, tubes, and stiffening plates inserted into the tubes together by inserting a flat tube provided with a stiffening plate of the direction of major axis into a fin and applying an internal pressure to a tube system. CONSTITUTION:The major diameter of a tube flat part 8 is made a slightly smaller than that of a fin 2 hole, and a stiffening plate 9 is set up in the inside of the tube. The assembling of fin tubes is performed by stacking up the necessary number of fins and inserting hair pin tubes 1 into the holes of fin 2. Tube bends 3 are welded to the tubes 1 after assembling the fins 2, tubes 1, and plates 9, to apply about an 100kg/cm<2> hydraulic pressure to the insides of tubes of a heat exchanger. In this way, the joining of fins 2, tubes 1, and plates 9 together of a heat exchanger consisting of thin wall-thickness flat tubes, impossible in the past, is stably performed, and the exchanger is made compact in size.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for manufacturing a flat tube heat exchanger, and in particular, a method suitable as a method for manufacturing a cross-fin-cheep type heat exchanger made of thin-walled tubes. It is related to.

[Background of the invention]

Heat exchangers with flat pipes are widely used in automobile radiators, etc. because they can greatly reduce the ventilation resistance of the heat exchanger, but they are still not in practical use in cross-fin tube heat exchangers such as room air conditioners. has not been standardized. This is because in radiators, etc., the fins and pipes are joined by welding, but in cross-fin tube heat exchangers, they are joined by expanding the pipes, so the difficulty in expanding flat pipes is due to the difficulty of expanding the flat pipes. This is because it is a major obstacle to its widespread use. Conventionally, tube expansion for fixing the fins of a cross-fin tube heat exchanger includes expansion using a rigid mandrel using a press and hydraulic expansion.

However, when the pipe is a flat pipe, pushing expansion using a rigid mandrel tends to cause the pipe to buckle toward the short diameter side.
Flat pipes have different curvatures in each part of the pipe wall, so there are differences in springback after expansion, and the disadvantage is that the contact thermal resistance between the fins and the pipe after expansion is larger than that of circular pipes. there were.

Furthermore, even if an attempt was made to expand a flat tube using hydraulic pressure, the flat tube would deform back into a circular tube, making it impossible to expand the tube.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for expanding tubes for manufacturing cross-fin tube heat exchangers having flat pipes with stable fixing force and high productivity.

[Summary of the invention]

First, by inserting a reinforcing plate in the long diameter part of the button to prevent the flat pipe from shrinking in the long diameter direction, it is difficult to return the thin flat pipe to a circular pipe, and it is relatively expensive, such as in the condenser of a refrigeration cycle. Patent application filed in 1984 for a heat exchanger that can be used even under pressure
This was proposed in No. 7654 and Japanese Patent Application No. 57-63843. The present invention provides that when a large pressure is applied to a flat pipe having a reinforcing plate having the above structure so that the outer periphery of the pipe is expanded, the shape of the flat pipe after pressurization is This method takes advantage of the fact that the pipe has a shape of two arcs, with the long diameter on the inner diameter side as the reinforcement, and the long diameter as the chord. The outer periphery of the pipe is expanded so that the short diameter side of the pipe is larger than the inner diameter of the short diameter side of the insertion hole formed in the fin, thereby firmly connecting the fin and the pipe. In this case, if the flat pipes are joined by welding pend pipes, it is possible to expand many pipes at the same time, and the reinforcing plate inserted into the pipes is also At the same time, it is designed to be firmly fixed.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows
This shows the appearance of a loss-fit, chain-type heat exchanger for room air conditioners.The heat exchanger is made of copper hairpin pipe 1.
．． Fin 2. It consists of a copper pen vibro.

As shown in FIG. 2, the fins are formed by pressing into a shape having a large number of pipe insertion holes 4 whose long diameters coincide with the ventilation direction (inlet direction in FIG. 2) when the heat exchanger Kg is installed. As shown in Fig. 3, the outline of the pipe insertion hole 4 is a circular arc r1 with the major axis 5 as the chord, and the corners are formed with a small circular arc r2 appropriately determined based on the pipe wall thickness, the thickness of internal reinforcement during expansion, etc. It is tied with A collar is formed in the pipe insertion hole 4 by drawing or ironing to ensure spacing between the fins, but depending on the size of r2, the collar may be completely formed around the entire circumference. In some cases.

Further, as shown in FIG. 4, the hairpin pipe 1 is made by bending it into a U-shape using a rotary drawstring, and then press-working the straight portion excluding the bent portion 7.
A flat portion 8 having substantially the same shape as the pipe insertion hole 4 of the fin 2 is formed.

FIG. 5 shows a cross section of the pipe flat section 8. As shown in FIG. The outside major axis of the tube is smaller than the major axis 5 of the fin hole 4 by a gap for assembly, and the shape of the tube is such that it can be assembled into the hole 4 of the fin. The reinforcing plate 9 is assembled inside the long diameter part of the flat pipe, but since the inner diameter of the pipe is shrunk to the width of the reinforcement when the pipe is expanded, it is desirable that the width of the reinforcement is as large as possible within the assembled range.

After stacking the required number of fins 2, the hairpin pipe 1 is inserted into the hole 4 of the fin 2 to assemble the fin pipe. The reinforcement 9 may be installed before or after the fin and pipe are assembled, but automation is easier if the pipe is assembled alone.

After assembling the fins, pipes, and reinforcing plates, weld the pen vibro and apply hydraulic pressure inside the heat exchanger tubes.

In this example, the tube has an outer diameter of 9.54 m and a wall thickness of 0.5 m.
Using 65-〇 steel pipe, the width is 12.0m as a reinforcing plate.
, 5PCC material with a wall thickness of 0.5 was used, and the hydraulic pressure was set to 100v-
By adding K, an increase in the circumference of 5 cm is obtained, and the major axis is 1
2. We were able to manufacture a heat exchanger with flat tubes with a short diameter of 77 mm, in which fins and tubes were firmly connected.

It should be noted that the same purpose can be achieved by forming the pipe 10 in advance into a corrugated cross-sectional shape as shown in FIG. 6 at a considerably lower pressure.

Furthermore, when expanding the short diameter 6 of the fin hole 4 by expanding the flat tube 8, the fin hole tries to maintain its outer circumferential length.
If the long axis 5 of the fin hole is shortened and the flat pipe length is expanded than the fin hole length, even if the long diameter of the pipe is reduced to the reinforcement width plus the pipe wall thickness, the fin and pipe will contact around the entire circumference of the contact area. contact thermal resistance can also be reduced. At this time, distortion occurs in the fins, but as shown in FIG. 7, in addition to the conventional slits 11 for heat exchange, fins/holes 4
By providing slits 12 and 13 in the fins to absorb strain when the tube is deformed due to tube expansion,
Distortion of the fins can be suppressed to a minimum, and the appearance of the heat exchanger and ventilation resistance can be prevented from being adversely affected.

〔Effect of the invention〕

According to the present invention, it is possible to connect the 7-in of a cross-fi/door tube heat exchanger made of 6,000 thin-walled pipes to the pipes and the reinforcement inserted into the pipes, which was previously impossible. At the same time, flat pipe heat exchangers can be formed in a stable state and there is no increase in contact thermal resistance, so flat pipe heat exchangers can be used in high-performance thin-walled and highly integrated heat exchangers such as room air conditioners, where flat pipes have not been used in the past. Great effects can be obtained in terms of reduction of energy consumption and downsizing of equipment.

[Brief explanation of drawings]

Figure 1 is an external view of a cross-fin cheep heat exchanger.
Figure 2 is an external view of the fins of a heat exchanger with flat pipes.
Fig. 6 is a plan view of the hole in the fin, and Fig. 4 is a plan view of the hole in the fin.
An external view of the embodiment, FIG. 5 is a sectional view of the flat part of the tube of one embodiment, FIG. 6 is a sectional view of the fin and tube assembly of another embodiment, and FIG. 7 is another embodiment. FIG. 1... hairpin pipe, 2... fin, 6... pend pipe, 4... fin hole, 5... fin hole length,
6... Short diameter of fin hole, 7... Bent part, 8... Pipe flat part, 9... Reinforcement plate, 10... Pipe flat part, 11
...Fin slit, 12...Fin slit, 1
6...Fin slit. Representative Patent Attorney Akio Takahashi’$1 Figure 6 $4 Figure

Claims (1)

[Claims] 1. After stacking a large number of fins with elliptical flat pipe insertion holes, insert a flat pipe into the fin's pipe insertion hole, the outside dimension of which is slightly smaller than the inside dimension of the fin insertion hole. It is characterized by assembling with a reinforcing plate inside that supports the long diameter, connecting the pipes with a pend pipe, and then applying internal pressure to the connected pipe system to fix the fins, pipes, and reinforcing plate inside the pipe at the same time. A method for manufacturing a heat exchanger.